Bone plates come in many sizes and shapes. The typical bone plate has a fixed dimension, and multiple holes for accommodating bone screws. In use, the surgeon brings together the fractured bone, places the bone plate atop the fracture, and inserts bone screws through the holes in the plate which overlie the healthy part of the bone, securing the bone about the fracture. Bone plates of many sizes are provided for the surgeon, and each is supplied with a number of holes so that the surgeon can arrange the plate over the fracture and have bone screw holes available above the healthy bone.
U.S. Pat. No. 6,666,867 describes a bone plate having an adjustable length. The adjustable length bone plate consists of a two parts, a first plate and a second plate, which are secured to the bone on opposite sides of the fracture. The first plate has laterally adjacent prongs which are inserted into the bore of a second plate. Bone screw holes are provided at the ends of the first and second plates to fasten them to the bone. The sliding bone plate has a locking mechanism, comprising a set screw passing through the second plate, and between the prongs of the first plate, fixing the length of the overall plate atop the fracture. The laterally adjacent prongs do not permit the surgeon to see the fracture surfaces coming together under the bone plate. Further, the use of only one locking screw permitted the assembled plate to twist longitudinally, permitting an unacceptable movement of the bone.
Orthopedic surgeons have also used DCP plates to stabilize fractured bone. The DCP plates also have openings for bone screws, and angulated openings, through which screws are “toed” into the bone, the tightening of the toed screws operating to move the bone, slightly, under the DCP plate. DCP plates have been used to move the bones on either side of the fracture closer together. This movement, however, was slight, and not easily controllable. Literally, the underlying bone is being pulled into place by the threads of a screw, providing no control over the twisting or turning of the bone, and the bending of the plate. In addition, the bone is pulled at an angle to the attached plates, resulting in a cocked bone, or an angle to longitudinal direction of the bone. This angulation, together with the micromotion in the bone, has lead to backing out of the screws.
It is an object of the invention to provide a two piece bone plate which is easy and inexpensive to manufacture.
It is a further object of the invention to provide a two piece bone plate which permits an observation window allowing the surgeon to see the bone surface coming together under the plate.
It is an object of the invention to provide a two piece bone plate which provides a strong locking mechanism for fixing the overall length of the plate, and resisting bending of the plate.
It is a further object of the invention to provide a bone plate which has an adjustable length, to permit the surgeon to fix the clinically effective length of the plate, permitting a better reconstruction or re-growth of bone at the fracture.
It is a further object of the present invention to provide a bone plate which resists bending, an thereby permits the surgeon better control of the movement of the underlying bone while adjusting the length of the plate.
It is still a further object of the present invention to provide a controlled method for bringing together the pieces of bone using a two piece bone plate, while controlling the turning of the bone.